9.做一个三角形的木架,以下四组木棒中,符合条件的是( )
| A. | 3cm,2cm,1cm | B. | 3cm,4cm,5cm | C. | 5cm,12cm,6cm | D. | 6cm,6cm,12cm |
5.如果整式x2+mx+9恰好是一个整式的平方,那么m的值是( )
| A. | ±3 | B. | ±4.5 | C. | ±6 | D. | 9 |
4.
如图,在△ABC中,BC=4,D、E分别是边AB和AC的中点,下面结论中不正确的是( )
0 286085 286093 286099 286103 286109 286111 286115 286121 286123 286129 286135 286139 286141 286145 286151 286153 286159 286163 286165 286169 286171 286175 286177 286179 286180 286181 286183 286184 286185 286187 286189 286193 286195 286199 286201 286205 286211 286213 286219 286223 286225 286229 286235 286241 286243 286249 286253 286255 286261 286265 286271 286279 366461
| A. | DE=2 | |
| B. | △ADE的面积与△ABC的面积之比为1:4 | |
| C. | △ADE∽△ABC | |
| D. | △DEC的周长与△ABC的周长之比为1:2 |